Epidemiological evidence that HTLV-III is the AIDS agent

Human T-lymphotropic virus type III (HTLV-III) is a recently discovered retrovirus with tropism and cytotoxicity for the OKT4+ lymphocytes that are depleted in the acquired immune deficiency syndrome (AIDS). In addition to the frequent detection of HTLV-III in patients with AIDS and related syndromes, seroepidemiological studies have shown that HTLV-III can be transmitted by sexual contact and blood transfusion in a manner identical to the putative AIDS agent. Analyses of stored sera have revealed that HTLV-III antibodies appeared in high-risk groups some two years before the disease outbreak, which corresponds to the apparent incubation period in patients with transfusion-associated AIDS. The risk of developing AIDS is clearly associated with HTLV-III seropositivity and may be as high as 20% within three years. Strong evidence that HTLV-III is the AIDS agent mandates aggressive efforts to minimize further sexual, maternal-fetal, and blood-borne transmission of this virus while pursuing vaccine development and antiretroviral therapies.